Leonardo da Vinci proposed a double hull to reduce the danger of leaks after a ship’s outer hull was damaged.
A double-hulled vessel has two layers of hull around part or all of its structure, creating a protective space between them. Leonardo’s maritime designs included ideas for improving ship safety and resistance to damage, anticipating a principle later used in specialized ships.
The concept does not mean that a ship has two separate boats placed together. The inner and outer structures work as layered protection, and the space between them can help keep water away from vital compartments when the outer skin is breached.
Modern double hulls became especially important in tanker design because they reduce the likelihood of cargo escaping after a collision or grounding. Leonardo’s sketch was an early expression of that broader engineering idea.